RF Bipolar Junction Transistors (BJT) are specialized semiconductor devices designed to amplify and switch high-frequency signals, typically in the radio frequency (RF) range from several megahertz to several gigahertz. Unlike standard BJTs, RF BJTs are optimized for low parasitic capacitance, high transition frequency (fT), and minimal noise, allowing them to maintain signal integrity at very high frequencies. These transistors are commonly constructed from silicon or gallium arsenide (GaAs) to provide high gain, linearity, and efficiency in RF applications.